Loyd’s Quest for the One Gigahertz Overclock

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A few weeks ago, we received a lovely care package from our PR friends at Intel: A G-stepping Q6600.

For those of you who don’t know, Intel’s recent G-stepping processors have resulted in lower power utilization. This is what enabled Intel to rate the dual core E6850 as a 65W TDP processor, even though it runs at 3.0GHz. The original, 2.93GHz X6800 dual core CPU was rated at 125W, then later at 75W. Now, the E6850’s TDP spec is a mere 65W.

The Q6600 is a quad core CPU based on Intel’s Kentsfield design. Having four cores turns up the heat a bit, so the G-stepping runs a little hotter, being rated at 95W TDP. That’s still an improvement over the original Q6600 shipped last January, which was rated at 105W.

This finally gave me impetus to do something I’ve wanted to do for some time: build an overclocking test bed. However, I didn’t want this to be the ultimate overclocking rig —partly because I wanted it to be easy to swap out parts. Here were the goals I set out for the system:

Roomy and easy to work inside

Relatively easy to swap out components

Focus mainly on CPU and memory

Be a human-scale system

That last one may seem a little weird, but what I mean by “human scale” is that this will be a system that mere mortals could build if they so choose. That precluded keeping a liquid nitrogen tank on hand, for example. It also precluded many less exotic liquid cooling systems as well. The idea of having to replace coolant every couple of years has never been something I found particularly appealing. All that tubing can be a big hassle.

On the other hand, I’m not fundamentally opposed to liquid cooling, provided it’s simple.

Also, this is a test bed for overclocking memory and the CPU, not pushing GPUs. Hey, it’s all about baby steps.

After ransacking the Ziff-Davis San Francisco office and my basement lab, this is what I ended up with a bill of materials:

CPU

G-Stepping Q6600 quad core CPU (default clock rate: 2.40GHz)

CPU Cooler

CoolIt Eliminator

Motherboard

XFX/Nvidia Nforce 680i

Memory

PNY XLR8 DDR2 1173 CAS5 2GB Kit

Graphics

ASUS EN8800 GTX Graphics Card

Case

Coolermaster Cosmos 1000

PSU

Coolermaster 850W quad-SLI certified

Hard Drives

2 x WD 150GB Raptor Hard Drives

Secondary Hard Drive

2 x WD 500GB, 7200RPM

Optical Drive

Lite-On 18x SATA DVD+/-RW

The PNY memory is actually a pretty good deal for DDR2 that’s rated at 1173MHz. However, remember that this is a test bed, so the memory isn’t going to be a fixed commodity.

The choice of CPU cooler was easy: the CoolIt Eliminator. This is hands-down the easiest liquid cooling solution I’ve ever installed. It’s relatively quiet, though I’m running it in performance mode. The Nvidia-designed and manufactured XFX board offers one of the most flexible—if a little arcane—BIOS setups I’ve seen.

Please understand, though, that I’m not endorsing any product. This is more like Loyd’s Toy, and any and all parts may change in the future.

Once I built up the system, I began trying to tweak it. One thing I quickly discovered is that the optional MCP cooling fan supplied with the motherboard is, in fact, not optional. If you try to overclock the CPU or memory even a little, the MCP temperature spikes pretty quickly. So the little clip-on fan is an essential item.

Since the Q6600 has a fixed multiplier that maxes out at 9x, the way to overclock is to futz around with the FSB (front side bus) clocks. Of course, you can push the FSB way high, and reduce the multiplier to 8x. One step at a time, however.

Mostly, I’ve been playing with different voltage settings (for memory and CPU, mostly), as well as FSB clocks. The memory is solid at 2.2v, and I’ve tweaked the CPU voltage up to about 1.45v. I think I’m going to have to go higher, though.

So far, the system is stable at an FSB clock of 366MHz (which is an effective FSB of 1464MHz.) This translates to a CPU clock frequency just shy of 3.3GHz. No matter what I try, I can’t get the system to be stable at anything higher.

Note that by “stable”, I mean it has to complete three runs of 3DMark06 and one run of PCMark05 without crashing or rebooting. Now, hitting 900Mhz over the rated clock rate for a 95W processor should make me happy, but I really, really, really would like to hit 1GHz. Just 100 more MHz

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